實體框架..Lambda表達（無法創建類型「System.Object的」恆定值）

Question

我要爲這個特殊的SQL查詢實體框架Lambda表達式查詢

 select Name from EmpMaster Where Code=163 

我試圖

string markedto= db.EmpMaster.Where(x => x.Code == 163).Select(x => x.Name).ToString(); 

但這給這個錯誤：

Unable to create a constant value of type 'System.Object'. Only primitive types or enumeration types are supported in this context

Answer 1

db.EmpMaster.Where(x => x.Code == 163).Select(x => x.Name)是IQueryable<string>。要從中獲取單個字符串值，請使用Single() ...

string markedto = db.EmpMaster 
        .Where(x => x.Code == 163) 
        .Select(x => x.Name) 
        .Single();